mirror of https://github.com/voidlizard/hbs2
25 lines
660 B
Haskell
25 lines
660 B
Haskell
module HBS2.OrDie where
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import Data.Kind
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import Control.Monad.IO.Class
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import System.Exit
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class OrDie m a where
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type family OrDieResult a :: Type
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orDie :: m a -> String -> m (OrDieResult a)
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orDieM :: (Monad m, OrDie m a) => a -> String -> m (OrDieResult a)
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orDieM a msg = pure a `orDie` msg
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instance MonadIO m => OrDie m (Maybe a) where
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type instance OrDieResult (Maybe a) = a
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orDie mv err = mv >>= \case
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Nothing -> liftIO $ die err
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Just x -> pure x
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instance MonadIO m => OrDie m ExitCode where
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type instance OrDieResult ExitCode = ()
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orDie mv err = mv >>= \case
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ExitSuccess -> pure ()
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ExitFailure{} -> liftIO $ die err
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